As the prior art in the technical field mentioned above, a mode-locked laser device disclosed in Patent Literature 1 has been known, for example. In the mode-locked laser device disclosed in Patent Literature 1, laser light modulated at a frequency which is an integer multiple of a frequency interval of a longitudinal mode occurring in a laser light resonator is amplified by a plurality of amplifiers (e.g., optical fiber amplifiers) having gains in respective spectral regions whose center wavelengths are different from each other, so as to produce a plurality of wavelength regions of pulsed laser light at once.